Viagra's 24-hour rival is launched

A new drug for male impotence which lasts for 24 hours or longer becomes available in Britain today.

The drug Cialis - a rival to Viagra, which is effective for only about four-and-a-half hours - is already known in France as "Le Weekend" pill.

Made by Eli Lilly, it works in the same way as Pfizer's Viagra, but Cialis is metabolised by the body slower and its effects last longer.

Dr John Dean, of Plymouth, a specialist in sexual medicine who has been involved in trials with the new drug, said that a complaint about Viagra was that couples needed to plan sex. "The manufacturers say that Cialis lasts for 24 hours but in the trials men said it could work for as long as 36 hours. Basically it gives couples more flexibility in their sex lives," he said.

Like Viagra, the drug will be available on the NHS for men whose impotence has a medical cause, for example erectile dysfunction because of diabetes, prostate disease, polio and injury. Or it can be obtained on a private prescription for £20, about the same price as Viagra.